Adjustable manhole cover assembly

ABSTRACT

An adjustable manhole cover frame assembly for mounting on a manhole basin upper section ( 12 ) has an outer ring ( 22 ) and an inner ring ( 20 ) engaging the outer ring by screw threads and supporting the manhole cover ( 10 ). The lower annular surface of the frame assembly rests on a convexly curved surface ( 36 C) of a metallic adapter ( 36 ), which in turn rests on the generally flat surface ( 12 A) of the manhole basin upper section ( 12 ); this allows the orientation of the frame assembly to be adjusted. Also, the frame assembly itself may have parts which allow its upper part to be adjusted for slope when the lower part of the frame assembly has been fixed. Another feature is a hinge mechanism ( 16 ) having a hinge arm ( 74 ) connecting two pivots ( 72,76 ), and having interlocking means ( 18 ) which prevent the hinge side of the cover from being raised when the cover is closed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional patent application No. 60/808,966 filed May 30, 2006, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a manhole cover assembly for mounting a manhole cover above a manhole basin and is especially applicable to manhole assemblies which allow adjustment of the slope of the manhole cover, and usually also its height, as necessitated by resurfacing a road surface and/or by frost-heave of the surrounding ground.

BACKGROUND ART

Manhole basins, which may be a sewer basin having an inlet and an outlet, or may be a catchment basin having only an inlet, are normally cast of concrete. A frame of metal is fixed to the top of the concrete basin and holds the manhole cover. In order to keep the cover level with a road or ground surface, it is frequently necessary to alter the height between the manhole cover and the top of the basin, particularly in regions where there is much frost heave; adjustment to the height is usually done when a road is resurfaced. Adjustment of slope may also be necessary, as when the camber of a road is changed. In addition, adjustment of the lateral position may be necessary, especially with catchment basins where the manhole must be positioned accurately close to a curb.

Various constructions of adjustable manhole frames have been proposed to deal with height adjustment and to avoid replacing concrete parts. In some cases, screw jacks have been used between the annular frame which holds the cover and the top of the concrete manhole basin. In other cases, an outer ring, supported by the basin, has internal helical threads of large diameter within which is an inner ring having mating screw threads, and which is rotatable to adjust its height. Examples of patents showing such arrangements are listed in my U.S. Pat. Nos. 6,179,518, issued Jan. 30, 2001, and 6,698,973, issued Mar. 2, 2004.

Many of the prior patents are concerned with height adjustment, and show little or no provision for slope adjustment. Most of the patents show upper and lower parts of the frame assembly to be connected by helical threads surrounding the annular upper portion of the frame so that rotation of this upper portion changes its height without any change to its slope. However, some other patents show jack-type screw adjusters which are spaced around the frame and which can be adjusted individually to alter the slope, as well as the height, of the upper frame portion. Such arrangements are shown in the following patents:

U.S. Pat. No. 3,930,739, which issued Jan. 6, 1976 to Larsson et al.;

U.S. Pat. No. 4,149,816, which issued Apr. 17, 1979 to Piso; and

U.S. Pat. No. 4,925,337, which issued May 15, 1990 to Spiess et al.

These prior arrangements would appear to have some drawbacks. In particular, they seem to offer only limited slope adjustment. This is especially true of Piso, where more than slight change of slope would seemingly cause binding in the adjusting screws. In Larsson et al. and Spiess et al., the amount of slope adjustment would be limited by binding between outer edges of the upper frame portion and the fixed surrounding structure. Also, these prior patents do not show any seals which would prevent ingress of soil or other material into the mechanical parts if there were to be significant slope adjustment. Larsson et al. and Piso show small seals which would accommodate only a small amount of slope adjustment, while Spiess et al. show no seal at all.

My aforesaid U.S. Pat. No. 6,698,973 shows an improvement in the prior designs that provides both height adjustment and slope adjustment of the cover frame. In the arrangement shown in that patent, a manhole basin of precast concrete has a top section with a convex part-spherical top which is engaged by a concave part-spherical outer lower frame part of the metallic frame assembly. The frame assembly includes an inner, upper frame part connected to the outer, lower frame part by screw threads. This upper frame part itself has upper and lower portions joined by part-spherical mating surfaces. The two pairs of part-spherical mating surfaces allow the inclination of the outer, lower frame part, and of the inner, upper frame part to be independently adjusted, so that both the inclination and the lateral position of the inner upper ring part can be varied. The height of the upper frame part is also adjusted by the conventional, helical screw threads.

While the invention of my U.S. Pat. No. 6,698,973 has been valuable, nevertheless it has the limitation that it envisions the use of a specially-shaped precast concrete manhole top section with the part-spherical top, or the use of a relatively heavy concrete adapter. I have found that there is a need for a device which can be used when it is not convenient to replace a conventional pre-cast top section with one similar to that of my U.S. Pat. No. 6,698,973.

DISCLOSURE OF INVENTION

The present invention seeks to overcome, or at least ameliorate, one or more of the disadvantages of these known arrangements, or at least provide an alternative.

In accordance with one aspect of the present invention, an adjustable manhole assembly comprises:

an adapter part having a lower, annular surface portion suitable for resting on a generally flat top surface portion of a manhole top section, the adapter having a part-spherical, upwardly convex metal upper surface,

and an adjustable frame assembly having an upper, inner frame movable within a lower, outer frame for adjusting the height of the inner frame, and wherein the lower, outer frame has an annular lower surface which mates with the upper part-spherical surface of the adapter.

Preferably, both of the mating surfaces are part spherical, or at least have similar sloping surfaces. Also, the mating surfaces are preferably surrounded by a sealing collar to minimize entry of soil or other matter between these surfaces.

While the assembly shown in my prior U.S. Pat. No. 6,698,973 was made of cast grey iron, the castings used in embodiments of the present invention preferably are of ductile iron. This allows the components to be thinner and stronger, this can reduce the weight by about one halt making the assembly more attractive to users.

As in my aforesaid U.S. Pat. No. 6,698,973, the upper, inner frame has an upper portion and a lower portion with mating surfaces, and at least one of these surfaces is part spherical, so that the upper portion of the inner frame may be adjusted in slope relative to the lower portion of the inner frame while maintaining a sealing relationship between the mating surfaces. Again, both of these upper mating surfaces are preferably part-spherical. The inner and outer frames have the conventional screw-threaded engagement which allow for height adjustment.

The lower mating surfaces between the manhole basin adapter section and the frame assembly provide a coarse slope adjustment, while the upper mating surfaces between the upper and lower portions of the upper, inner frame provide a fine slope adjustment.

In my U.S. Pat. No. 6,698,973, the outer surface of the outer frame part has a concrete collar which contacts a sealing collar, this sealing collar allows the outer frame to rise while still maintaining at least a partial seal between the outer frame and the part-spherical surface on which it rests. This seal is improved with the present construction, since here there is no concrete collar, but instead at least a lower portion of the outer frame has a machined metal surface, and the sealing collar has a resilient O-ring in contact with this metal surface, and so maintains a good seal during its movement relative to the outer frame.

The adapter part comprise a lower adapter section and an upper adapter section, the lower adapter section providing said lower, annular surface for resting upon said flat top surface of the manhole and the upper adapter section providing said part-spherical, upwardly convex upper surface, lower and upper surfaces of the upper and lower adapter sections, respectively, being configured to permit adjustment of the angle between the upper adapter section and the lower adapter section so as to adjust the inclination of the part-spherical, upwardly convex upper surface relative to said top surface.

The lower adapter section may have a part-spherical inner diverging upwardly and outwardly and the upper adapter section have a lowermost peripheral edge with a diameter such that the circumferential lower edge of the upper adapter section rests in and is slidable relatively to the part-spherical inner wall to permit tilting of the upper adapter section relative to the lower adapter section.

A manhole assembly embodying the first aspect of the invention may be used in a process to adapt existing manholes to accommodate differing cambers of roads. Thus, in accordance with another aspect of the present invention, a method for providing an adjustable manhole assembly comprises the steps of:

providing a generally flat top surface portion of a manhole top section,

placing on said top section an adapter part having a lower, annular surface portion suitable for resting on said flat top surface portion, the adapter having a part-spherical, upwardly convex metal upper surface,

and placing on said metallic adapter part an adjustable frame assembly having an upper, inner frame movable within a lower, outer frame for adjusting the height of the inner frame, said lower, outer frame having an annular lower surface which mates with the upper part-spherical surface of the adapter.

Embodiments of the invention may also employ a special hinge with a locking arrangement for locking the manhole cover in place on the frame assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which;

FIG. 1 is a top view of a manhole cover, a man hole cover frame assembly and an adapter;

FIG. 2A is a sectional elevation of the upper part of a manhole basin having the adjustable manhole cover frame assembly and adapter mounted on a manhole basin top section, with the cover closed;

FIG. 2B is an enlarged view of a portion of FIG. 2A showing a hinge;

FIG. 2C is an enlarged view of a portion of FIG. 2A showing a locking mechanism;

FIG. 2D is a detail cross-sectional view of the locking mechanism modified by inclusion of an anti-vibration cap for the head of a shaft of the locking mechanism;

FIG. 2E is a perspective view of a shaft of a locking element;

FIG. 2F is a perspective view of the cap adapted to fit the head of the locking element shaft;

FIG. 2G is a detail cross-sectional view taken on line G-G of FIG. 2D;

FIG. 3 is an exploded view of components of the frame assembly, and including the adapter;

FIG. 4 is an enlarged view of the adapter and portions of the frame assembly, showing the slip joint between the lower, outer frame and the adapter;

FIG. 5A is an enlarged view of a top portion of the frame assembly showing the joint between the upper and lower portions of the upper, inner frame;

FIG. 5B is a view of parts similar to those of FIG. 5A but taken at a different circumferential position around the frame assembly;

FIG. 6 is a detail view of the hinge between the manhole cover and the upper, inner frame, with the cover open;

FIG. 7 is a view of the underside of the manhole cover assembly with the cover closed;

FIG. 8A is a side view of a modified adapter part having a lower adapter section supporting an upper adapter section in a level position;

FIG. 8B is a side view of the modified adapter part supporting the upper adapter section at a maximum tilt angle relative to the manhole top section;

FIG. 8C is a perspective view of the upper adapter section;

FIG. 8D is a plan view of the lower adapter section; and

FIG. 8E is a perspective view of the lower adapter section.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

FIGS. 1 and 2 show a manhole cover 10 supported on the top section 12 of a manhole basin by a manhole cover frame assembly 14 which is adjustable. The manhole basin, of which the top precast section 12 is shown partially in FIG. 1, is cast of concrete, and rests on middle and lower sections which are not shown. The frame assembly 14 allows adjustment of the height and slope of the cover 10 relative to the ground level G. The cover is connected to the frame assembly 14 on one side by a hinge indicated at 16, and, when closed, is connected to the other side of the frame assembly 14 by a locking mechanism indicated at 18; details of the hinge and locking mechanism are given below.

The frame assembly 14, in common with some prior art designs, has two parts formed of cast metal, firstly an upper, inner frame part 20, and secondly a lower, outer frame part 22. The upper frame 20 has an external helical screw thread 24 which engages an internal screw thread 26 of the lower frame 22. The upper frame screw thread 24 subtends just one complete 360° circle. Rotation of the upper frame relative to the normally stationary lower frame adjusts its height in accordance with prior art procedures; for example, as disclosed in my U.S. Pat. No. 6,698,973, to which the reader is directed for reference and which is incorporated herein by reference. The rotation can be done by conventional methods, for example by use of a special tool having depending spigots which fit into bores in the top of the upper frame 20.

The upper, inner frame 20 has an inwardly projecting flange 28 and an upstanding, surrounding flange 30, which flanges provide a recess for receiving the edge portion of the manhole cover 10. The underside of the outer edge portion of the cover 10 has a groove 32 which receives a sealing gasket 34 (FIG. 2A).

The top precast section 12 has an annular flat top 12A. On this rests a generally flat, annular lower surface 36A of an adapter 36, which is a hollow, ductile iron casting having a circular central aperture 36B slightly smaller in diameter than the interior of upper inner frame 20, and an outer surface 36C which is of convex, part-spherical form. The part-spherical surface 36C has a center of curvature below the spatial center of the manhole top section 12. On this surface 36C rests the lower rim 22A of lower, outer frame 22, such lower rim having an outwardly diverging surface having a slope similar to the slope of the surface 36C.

As best seen in FIG. 4, the mating surfaces are surrounded by a sealing collar 38 having a cylindrical part 38A lying against the outside of outer frame 22 and a flared skirt part 38B lying against the part-spherical upper surface 36C. This sealing collar 38 may be made of glass fiber reinforced polyester, and preferably includes upper and lower internal annular recesses which accommodate, respectively, O-rings 42A and 42B which contact the outer surface of outer frame 22 and the upper surface 36C of the adapter 36. The recesses holding the O-rings have openings which are narrower than the width of the unstressed O-rings so that the O-rings do not fall out. This collar 38 is intended to largely prevent soil or other dirt from entering between the mating surfaces, especially when frost lifts the outer frame 22, and also prevents infiltration of ground water when the water table is high. The ground which has been back-filled on top of the lower part 38B of the collar 38 prevents this rising if the outer frame 22 rises with frost, with the lower part of the outer frame sliding against the O-ring 42A. To allow this motion, the lowermost few inches of the outer frame 22 are machined to a smooth surface. The rising and falling of the outer frame part can prevent potholes usually caused by frost heave or ground movement, and consequently reduces the cracking asphalt and reduces the need for road repairs.

Referring to FIGS. 5A and 5B, the upper, inner frame 20 itself is formed of upper and lower portions 20A and 20B, which are also joined by part-spherical mating surfaces. These surfaces include a concave surface 44B in lower portion 20B, and a convex surface 44A on the underside of upper ring portion 20A. Each of these surfaces has a center of curvature above the center of the manhole cover 10, Details of the joint are shown in FIGS. 5A, 5B and 6, which show enlarged views of the mating parts. As shown, the upper frame flange 28 is effectively split to provide these part spherical mating surfaces 44A and 44B.

As shown in FIG. 5B, the upper part 28A of this flange, which is integral with the upper frame portion 20A, has a series of countersunk bores 46 for receiving the heads of screws 48. The arrangement is similar to that described in my aforesaid U.S. Pat. No. 6,698,973, and which is shown in detail in FIGS. 2A and 2B of that patent. However, one difference here is that the lower portions of bores 46 diverge downwards so that the screws 48 can remain vertical when the adjustments are made. The screws 48 pass through enlarged apertures 46A in the lower part of the flange 28B which is integral with the lower frame portion 20B, the screws then passing through washers 50 and being secured by nuts 52. The washers 50 are elliptical, being elongated in the circumferential direction so that they can engage the flange 28B at two opposed sides of the apertures 46A, while allowing the screws to come close to the radial outer side of the apertures. These large apertures 46A for the screws 48 allow radial movement of the screws 48 when they have been loosened to allow adjustment of the upper frame portion 20A on the lower frame portion 20B between the co-axial position shown in FIG. 5A and an eccentric position. Since diverging bores 46 allow the screws 48 to remain vertical, there is no need for an extra washer to accommodate misalignment. However, since the alignment of screws 48 needs to change with respect to the flange 28A, the lower surfaces of the screw heads 48A, and the corresponding upper face of the enlarged portion of the countersunk bore 46, have complementary convex and concave surfaces.

In order to exclude dirt and asphalt from between the outer frame 22 and the inner frame 20, inner and outer cylindrical sealing collars 54A and 54B are provided surrounding the outer top flange 30 of the upper portion 20A of inner frame 20. The sealing collars 54A and 54B, rest on the top of upper flange 54A projecting both outwardly and inwardly from the top of lower, outer frame 22. These collars 54A,54B may be of medium density 5 mm thick polyethylene. The collars are resilient enough to accommodate the movement of the upper frame portion 20A relative to the lower frame portion 20B. The movement of the upper frame portion 20A will usually be limited to about 3° or 0.5 cm; the greater movement occurs between the mating surfaces 34B and 36C.

During re-surfacing of the road for height adjustment, the inner cylindrical sealing collar 54A will be removed from its housing, after taking out the upper ring portion 20A with its flange 28A; then the inner frame 20 becomes easily rotatable for height adjustment. The outer cylindrical sealing collar 54B remains fixed, because it sticks to the asphalt. The collars 54A and 54B prevent dirt and asphalt entering the threads between the outer and inner frames.

The outer portions of flange 56A engage the ground, and can cause the outer frame 22 to remain stationary relative to the upper layer of ground during frost heave, so that the assembly is partly self-adjusting to changes in ground level. Under the outer portions of flange 56A are two triangular projections 58B and 58C, arranged on opposite sides of the outer frame about 180° apart, and which are formed with the outer frame during casting. These are termed “frost wings” and serve to engage the ground and resist rotation of the outer frame 22.

A “Teflon”™ paint or equivalent lubricant may be used between the upper mating surfaces of the portions 20A and 20B, as well as around the screw threads 24 and 26, to make for easier sliding, both when adjusting the slope and when rotating the inner frame 20 to adjust the height.

FIGS. 2C and 5A show other mean for securing the inner frame 20 relative to the ground. In particular, the outer top flange 30 has apertures 60 spaced around its periphery, and these receive spikes 62 which are driven radially outwardly through the two layers of the plastic collars 54 and into the surrounding asphalt/ground.

As shown in FIG. 4, a dirt-excluding plastic barrier skirt 64 is suspended from a fiber ring 66 which hangs from an inner land 68 formed at the bottom of the upper, inner, frame 20. This skirt 64 tends to exclude dirt from the sliding surfaces forming the joint between the lower rim of lower frame 22 and the adapter 36.

The hinge 16 shown in FIGS. 2A, 2B, 6 and 7 has a novel configuration in that it comprises internal hinge which, unlike some prior art hinges for manhole covers, is not exposed to road dirt.

As shown in FIGS. 2B, 6 and 7, hinge 16 includes a spaced pair of brackets 70 fixed to the inner surface of lower flange 28, these brackets supporting ends of a pivot pin 72, the central portion of which carries an angled hinge arm 74, movable between the brackets. This hinge arm has an inner portion 74A with its inner end pivoted to bracket 70, and which slopes downwardly from this pivot pin 72 when the cover 10 is closed, and an outer portion 74B extending from portion 74A at an obtuse angle so as to slope upwardly in the cover closed situation. As shown in FIGS. 2A, 2B and 7, the outer end of portion 74B carries a cross pin 76 protruding from its sides, end portions of the cross pin 74 being slidingly received in slots 78 of parallel guide members 80 extending along, and fixed to, the lower surface of the cover 10. This combination provides a loose fitting type of hinge which allows the cover to find its proper sealing position when closed, without need to carefully align the hinge parts. The bent nature of the hinge arm 74 allows this to avoid interference with the flange 30 when the cover 10 has been pivoted through 180° from the closed position into the fully open position shown in FIG. 6; the 180° of movement allowing the cover 10 to lie on ground adjacent to the manhole, where there is no danger of it falling.

Normally, a loose fitting hinge as so far described would allow the hinged end of the cover 10 to be opened a small amount, even if the other end of the cover 10 were locked to the underlying frame as by lock 18. Nowadays, with the prospect of terrorists inserting explosives or other material into manholes, it is most desirable that it should not be possible to raise the hinge end of the cover to any appreciable extent. Accordingly, the ends of the guide members 80 closest to the edge of the cover 10 are provided with locking elements 82 which project away from the lower surface of the cover 10, this being the uppermost surface when the cover 10 is fully open, as in FIG. 6. These locking elements 82 have camming surfaces 82A facing the effective hinge axis formed by pivot pin 72, and these camming surfaces are designed to cooperate with inwardly and downwardly sloping undersurfaces 70A of the pivot brackets 70 so that, when the cover 10 is closed as in FIGS. 2A, 2B and 7, the surfaces 70A and 82A are close to each other or in contact, and prevent the cover 10 from being lifted at its hinge side.

The locking mechanism 18 is shown in detail in FIG. 2C and, with a slight modification, in FIG. 2D; this is similar to that used in my aforesaid '973 patent, but somewhat simplified as to the form of flange 28A. As shown, the upper frame portion 20A has its flange 28A provided with a recess 84 in its inner surface, the recess providing an upper recessed undersurface 84A. This recess 84 accommodates a D shaped locking element or pawl 86 so that the pawl 86 engages the undersurface 84A to prevent opening of the cover 10. The pawl 84 is carried by a vertical shaft 88 which is rotatably held in a vertical bore 90 (FIG. 2D) near the outer edge of the cover 10. The top of the shaft 88 has a non-circular head 92 for receiving a key for rotating the shaft 88 and for locking or unlocking the cover 10. As can be seen from FIG. 2D, the head 92 takes the form of a socket having an external flat 92A and a pentagonal socket 92B with a central pin 92C.

The uppermost portion of the vertical bore 90 opens into a generally cylindrical bore extension portion 90A which accommodates the head 92 and a surrounding resilient cap 94, conveniently of synthetic plastics material. As shown in FIG. 2F, the bore extension portion 90A has a flat 92B which engages a corresponding flat 94A on the exterior of the cap 94 and the interior of the cap 94 has a flat 94B which engages the flat 92A on the exterior of the socket head 92. The cap 94 is resilient and is sized to grip the socket head 92 and the interior of bore extension 90A so that it is not dislodged by vibration caused by traffic. The flats 92A, 94B, 94A and 90B cooperate to prevent rotation of the locking shaft 88 and locking element 86 and consequent unlocking of the mechanism 18 as a result of such vibration.

Whereas FIG. 2A shows the locking pawl 86 secured to the shaft 88 by a nut, in FIGS. 2D and 2E the shaft 88 is shown with a square end 88A which receives the locking pawl 86 and has a transverse hole 96 to receive a split pin to secure the locking pawl 86 to the shaft 88.

As can be seen from FIG. 2D, the depth of the bore extension 90A is sufficient to ensure that the top of cap 94, when fully inserted, is lower than the surface of cover 10. Also, the recess 84 is spaced well below the seal between the cover 10 and the flange 28, and so there is no interference between the lock and the seal.

It will be appreciated that additional, similar locking mechanisms 18 could be provided, spaced apart around the edge of the cover 10.

In use, the mating surfaces 24B and 36C between the adapter 34 and the frame assembly 14 may be used to allow the frame assembly to be orientated so that its cylindrical axis is vertical even if the concrete parts, after back filling, are found to be tilted. The upper mating surfaces, between the upper frame portions 20A and 20B, are usually adjusted at a later stage, after resurfacing of a road has occurred, if it is found that slope adjustment is needed. This involves loosening screws 48, moving the upper portion 20A so that screws 48 slide along the apertures 46 and then tightening the screws. The upper, inner frame part 20 can also be rotated as needed to bring the manhole cover up to the road level.

While the manhole frame assembly described with reference to FIGS. 1 to 7 will provide sufficient inclination adjustment for most applications, even more inclination adjustment may be obtained by employing an adapter part comprising a pair of adjustable elements allowing the tilt angle between the uppermost of the pair of elements and the concrete 12 to be adjusted.

Thus, referring to FIG. 8A to 8E, the adapter part comprises two sections, namely an upper adapter section 36′ similar to that shown in FIGS. 1 to 7, and a lower adapter section 36″. The lower adapter section 36″ comprises an annular part-spherical metal dish-like element interposed between the upper adapter section 36′ and the top surface 12A of the concrete top section 12 of the manhole. The central hole of the lower adapter section 36″ is substantially equal to the inner diameter of the top section 12. The height of the lower adapter section 36″ varies uniformly between a maximum and a diametrically opposite minimum. The maximum height is approximately double the minimum height.

The diameter of the lower edge of the upper adapter section 36′ is slightly less than the horizontal diameter of the lower adapter section 36″ at its minimum height, so that, when level, the upper adapter section 36′ rests inside the lower adapter section 36B with its lowermost edge in contact with the part-spherical surface along a line just below the minimum height position. As shown in FIG. 8B, the upper adapter section 36′ can be tilted until its lowermost edge contacts the lower adapter section 36″ along a line between the maximum height at one side and the minimum height at the opposite side.

Tilting of the upper adapter section 36′ relative to the lower adapter section 36″ is in addition to the tilting of the outer frame 22 relative to the upper adapter section 36′. Consequently, the two-piece adapter part 36′/36″ allows the outer frame 22 to be tilted relative to the top surface 12A by as much as 24-30 degrees from the horizontal position, as shown in FIG. 8B.

While reducing the height of the dish member at one side restricts the range of directions in which the adapter can be tilted, it saves material. Of course, if omnidirectional tilting is desired or required, the height of the lower adapter section 36″ could be uniform.

FIGS. 8A and 8B show the lower adapter part 36″ surrounded and supported by in-fill 100 which is intended to prevent soil from entering between the lower adapter section 36B and the underlying top surface 12A and allowing frost-heave to lift the lower adapter section 36″. The in-fill 100 may comprise concrete or mortar applied around the lower adapter section 36″ during installation. Alternatively, it may be formed around the part-spherical lower adapter section 36″ during manufacture and the resulting two-piece lower adapter section, having a part-spherical metal upper surface, flat annular concrete/mortar lower surface and generally cylindrical outer surface, shipped to the installation location as one unit.

It is also envisaged that a greater range of height adjustment may be provided by interposing one or more spacer rings between the components shown in FIG. 3; for example between the inner frame lower portion 20B and the outer frame 22.

INDUSTRIAL APPLICABILITY

Manhole assemblies embodying the present invention allow adjustment of the slope and height of the manhole cover, as necessitated by resurfacing a road surface and/or by frost heave of the surrounding ground. They may allow adjustment of the lateral position of the manhole cover. To some extent the manhole cover may be self-adjusting. Manhole assemblies embodying the invention also may have an improved self-levelling feature which better allows automatic height adjustment when the road level rises, for example due to frost. 

1. An adjustable manhole cover assembly comprising; an adapter part (36) having a lower, annular surface portion (36A) suitable for resting on a generally flat top surface (12A) of a manhole top section (12), the adapter part having a part-spherical, upwardly convex metal upper surface (36C), and an adjustable frame assembly (14) having an upper, inner frame (20) movable within a lower, outer frame (22) for adjusting the height of the inner frame, and wherein the lower, outer frame has an annular lower surface (22B) which forms a mating surface slidable on the upper part-spherical surface (36C) of the adapter and which provides a joint between the adapter (36) and the outer frame (22).
 2. A manhole cover assembly according to claim 1, wherein the lower mating surface (22B) has a slope similar to that part-spherical surface (36C) of the adapter part (36).
 3. A manhole cover assembly according to claim 1, wherein the upper, inner frame (20) has an upper portion (20A) and a lower portion (20B) with respective mating surfaces, and at least one of these surfaces is part-spherical, whereby the upper portion (20A) of the upper, inner frame (20) may be adjusted in slope relative to the lower portion (20B) of the upper inner frame (20) while maintaining a sealing relationship between the last-mentioned mating surfaces.
 4. A manhole cover assembly according to claim 1, wherein said metallic adapter part (36), and said inner and outer frames (20, 22) are made of ductile iron.
 5. A manhole cover assembly according to claim 1, wherein at least a lower portion of said outer frame (22) is provided with a machined cylindrical metal surface, and a sealing collar (38) is provided covering said joint between the mating surfaces of the outer frame (22) and the adapter (36), said collar having means (42B) for sealing against said machined lower portion of the outer frame, which sealing means allows said outer frame to slide upwardly in said collar, under the influence of frost-heave or like forces lifting the outer frame, while maintaining a seal over said joint.
 6. A manhole cover assembly according to claim 1, comprising a hinge mechanism (16) for connecting one side of a manhole cover (10) to said inner frame (20), and having locking means (18) for locking the other side of the cover (10) to the inner frame (20), said hinge mechanism comprising; bracket means (70) fixed to an inner surface of said inner frame (20) and positioned to be covered by the cover (10) when closed, said bracket means supporting a pivot (72); a hinge arm (74) having an inner end carried by said pivot; further pivot means (76) connecting an outer end of the hinge arm to the underside of the cover (10); a downwardly facing cam surface (68A) carried by said upper, inner frame (20) adjacent to said bracket means (70); and a locking element (82) carried by the underside of said cover and positioned so that, in the closed position of the cover, said locking element fits against the underside of said cam surface (68A) and prevents the hinge side of the cover from being raised when the other side of the cover is held closed by said locking means.
 7. A manhole cover assembly according to claim 6, wherein said further pivot means (76) connecting the outer end of the hinge arm (74) to the cover (10) includes a pivot pin carried by said hinge arm (74), said pivot pin being slidable in slots (78) carried by guide members (80) fixed to the underside of the cover, the arrangement being configured to allow the cover to be opened through substantially 180° of pivoting so that the cover can rest on level ground next to the said frame assembly.
 8. A manhole cover assembly including an upper frame (20) and a manhole cover (10), a hinge mechanism (16) for connecting said cover to one side of said upper frame, and having locking means (18) for locking the other side of the cover to the upper frame, said hinge mechanism comprising; bracket means (70) fixed to an inner surface of said upper frame and positioned to be covered by the cover when closed, said bracket means supporting a pivot (72); a hinge arm (74) having an inner end carried by said pivot; further pivot means (76) connecting an outer end of the hinge arm to the underside of the cover; a downwardly facing cam surface (68A) carried by said upper frame adjacent to said bracket means; and a locking element (82) carried by the underside of said cover (10) and positioned so that, in the closed position of the cover, said locking element fits against the underside of said cam surface and prevents the hinge side of the cover from being raised when the other side of the cover is held closed by said locking means.
 9. A manhole cover assembly according to claim 8, wherein said further pivot means (76) connecting the outer end of the hinge arm to the cover includes a pivot pin (76) carried by said hinge arm, said pivot pin (76) being slidable in slots (78) carried by guide members (80) fixed to the underside of the cover, the arrangement being configured to allow the cover to be opened through substantially 180° of pivoting so that the cover can rest on level ground next to the said frame assembly.
 10. A manhole cover assembly according to claim 1, wherein said upper frame (20) has an upstanding flange (28) surrounding a recess for the manhole cover (10), and said flange has apertures (60) spaced around its periphery, said apertures being suitable for receiving spikes (62) which can be driven into the ground surrounding the upper frame to secure the upper frame to the ground.
 11. A manhole cover assembly according to claim 6 comprising an anti-rotation device (94) for preventing unlocking of the locking mechanism (18) as a result of vibration.
 12. A manhole cover assembly according to claim 11, wherein the anti-rotation device (94) acts between the locking element (86,88) and the cover (10) to prevent relative rotation therebetween.
 13. A manhole cover assembly according to claim 12, characterize in that wherein the locking element (88) has a socket head (92) having an external flat (92A) and accommodated, in use, within a hole (90) in the cover (10) the hole having an internal flat (90B), and the anti-rotation device comprises a cap (94) adapted to fit between the socket head and the surrounding hole and having internal and external flats (94B,94A) for engaging, respectively, the socket head flat and the flat of the hole, to prevent unlocking of the locking member by rotation of the locking element relative to the cover.
 14. A manhole cover assembly according to claim 13, wherein the cap (94) is resilient and sized to engage either or both of the socket head (92) and the hole (90) so as to inhibit dislodging of the cap as a result of vibration caused by traffic.
 15. A method for providing an adjustable manhole assembly comprising the steps of: providing a generally flat top surface portion of a manhole top section, placing on said top section a metallic adapter part having a lower, annular surface portion suitable for resting on said flat top surface portion, the adapter having a part-spherical, upwardly convex upper surface, and placing on said metallic adapter part an adjustable frame assembly having an upper, inner frame movable within a lower, outer frame for adjusting the height of the inner frame, said lower, outer frame having an annular lower surface which mates with the upper part-spherical surface of the adapter.
 16. A manhole cover assembly as claimed in claim 1, wherein the adapter part (36) comprises a lower adapter section (36′) and an upper adapter section (36″), the lower adapter section (36″) providing said lower, annular surface (36A) for resting upon said flat top surface (12A) of the manhole and the upper adapter section (36′) providing said part-spherical, upwardly convex upper surface (36C), lower and upper surfaces of the upper and lower adapter sections, respectively, being configured to permit adjustment of the angle between the upper adapter section and the lower adapter section so as to adjust the inclination of the part-spherical, upwardly convex upper surface relative to said top surface.
 17. A manhole cover assembly as claimed in claim 16, wherein the lower adapter section (36″) has a part-spherical inner wall diverging upwardly and outwardly, the upper adapter section (36″) having a lowermost peripheral edge with a diameter such that the upper adapter section rests in and is slidable relatively to the part-spherical inner wall.
 18. A manhole cover assembly as claimed in claim 16, wherein the height of the lower adapter section varies from a maximum at one side to a minimum at a diametrically opposite position.
 19. A manhole cover assembly according to claim 8, wherein said upper frame (20) has an upstanding flange (28) surrounding a recess for the manhole cover (10), and said flange has apertures (60) spaced around its periphery, said apertures being suitable for receiving spikes (62) which can be driven into the ground surrounding the upper frame to secure the upper frame to the ground.
 20. A manhole cover assembly according to claim 8 comprising an anti-rotation device (94) for preventing unlocking of the locking mechanism (18) as a result of vibration. 